The prevalence of diabetes and its associated vascular complications were assessed in several Pacific Island populations, including Polynesians and Melanesians, living in traditional ways as well as in urbanized communities. These investigations were designed to compare and contrast the rates of diabetes in different ethnic groups living in similar environments and to examine differences in the same ethnic groups living in different environments in order to determine the extent of the possible influences of both genetic factors and environmental determinants on the occurrence of diabetes. In general, much higher prevalences of diabetes and the associated complications were found in the urbanized populations, and attempts to determine the reasons for these differences are being pursued. Increased obesity, reduced physical activity, changes in dietary composition and intake appear to contribute to these differences in frequency, but genetic factors also are likely important in determining the frequency of the diabetes, itself, and possibly the type and frequency of associated complications. Identification of the relative importance of environmental determinants of diabetes is a prerequisite to formulating preventive measures for this disease in developing countries. The fortuitous occurrence of epidemic polyarthritis, caused by Ross River virus infection, led to a detailed description of the disease, including redefinition of the incubation period and the discovery of new vectors for the disease. A follow-up study was conducted and determined that infection during pregnancy resulted in no fetal or congenital complications.